Function Development - Brainstorm

[AndersAskeland]

Previous section

The preceding section is: sessions/package-setup.qmd.

During this section, participants learn about setting up and preparing the R environment for creating packages.

Learning outcome

Overarching goal

• Learn to create and structure functions that can be effectively utilized within R packages.

Sub goals

• Develop code interactively (exercise 1) and transform it into robust functions (exercise 2).
• Understand and apply function abstraction to enhance modularity and reusability (exercise 3).
• Master dependency management within package development (exercise 4).
• Implement process control and error handling to ensure function reliability (exercise 5).

Exercises

The following exercises are designed to develop a comprehensive understanding of function development in relation to R package creation. The order should be adjusted based on the flow of the course.

Exercise 1 - Write Code/Script

Objective: Write a script that addresses a specific problem, showcasing the practical application of R code.

• Provide a specific scenario or problem statement for participants to solve.
• Offer a ready script/code snippet if time is short.

Note: If previous sections create functions/code - use this.

Exercise 2 - Rewrite Code into a Function

Objective: Convert the given script into a function.

• Emphasize aspects such as function naming, argument structuring. Documentation comes later.
• Code should be hard coded

Exercise 3 - Abstractions

Objective: Evolve the function by abstracting the action of extracting elements, enhancing its flexibility and reusability.

• Use examples to demonstrate the transition from specific implementations to abstracted functionalities.
• Place function in utils?

Exercise 4 - Dependency Management

Objective: Learn to accurately declare and manage package dependencies.

• Introduce and explain the use of Imports, Depends, and Suggests in the DESCRIPTION file.
• Provide examples of how to manage dependencies correctly and the consequences of poor management.
• Attach package/function?

Exercise 5 - Error Handling/Control Flow

Objective: Incorporate error checking and control structures within functions.

• Detail the use of stop(), warning(), and message() for providing feedback at various levels.

For example:

• There is not title/author/etc.
• Input is not "correct"/text.

Extra Exercise - Extending Generic Functions

• Custom print method?
• Probably too complex.

Optional Reading

• Control flow - Loops. Are often needed in functions that interact with other systems (i.e. servers, http requests, etc.)

Next Section

Documentation

[AndersAskeland]

Consider using cli() for error "documentation" according to the Tidyverse style-guide (https://style.tidyverse.org/error-messages.html#problem-statement).

[AndersAskeland]

Is there a need for participants to learn about breaks (break() & next())?

Don't see any real use for it as such (in the scope of the exercises), but could perhaps be a extra reading task or a reference?

[AndersAskeland]

Great quote related to complex functions: "When I look at that function signature I hear the screams of matrices being ground to a fine powder of bits through the conical burrs of nested for loops, and laboured index arithmetic." https://www.milesmcbain.com/posts/data-analysis-reuse/

[AndersAskeland]

Idea for a section/anti-session: "One function to rule them all"

[AndersAskeland]

Quote: "Packages are a way of describing and distributing functions in a structured and consistent way."

[AndersAskeland]

Exercise 5 - Give an unsupported variable to function, and see error. It is not easy to know what it means

[lwjohnst86]

I don't know why I wasn't shown these notifications 🤔. In relation to your question about break etc, I agree, I don't think that's necessary.